KR100630358B1 - Method for improving accuracy of multiple input multiple output channel measure - Google Patents

Abstract

A method for improving accuracy of MIMO channel measurement is provided to exactly measure an MIMO channel without interference by measuring maximum delay spread of the channel by using a Gold code or a Kasami code, and then selecting an LS code having a proper IFW(Interference Free Window) according to the measured maximum delay spread, thereby accurately measuring the channel without using a TDM(Time Division Multiplexing) structure. A method for measuring a MIMO(Multiple Input Multiple Output) channel comprises the following steps of: detecting the maximum value of maximum delay spread on each path, composing the MIMO channel, by using specific code information transmitted through a pilot signal(S302); selecting LS(Loosely-Synchronous) code information, satisfying a specific condition, as much as the number of receive antennas by using the detected maximum value, and then transmitting the selected LS code information to a transmission stage(S304); and receiving final LS code information, selected by using the LS code information, from the transmission stage, and then measuring the MIMO channel(S308).

Description

Method for Improving Accuracy of Multiple Input Multiple Output Channel Measure}

1 is a diagram illustrating a transmitting antenna and a receiving antenna in a conventional MIMO channel environment.

2 is a diagram for describing autocorrelation values and cross-correlation values of LS codes.

3 is a view for explaining a method of increasing the accuracy of the MIMO channel measurement according to an embodiment of the present invention.

4 is a block diagram illustrating an internal configuration of an apparatus for estimating a channel shock response and calculating a maximum delay time value for each path of a MIMO channel using a Gold code according to an embodiment of the present invention.

5 is a block diagram illustrating an internal configuration of an apparatus for measuring a MIMO channel by transmitting LS code information from a transmitter to a receiver according to an embodiment of the present invention.

The present invention relates to a method for increasing the accuracy of MIMO (Multiple Input Multiple Output, hereinafter referred to as 'MIMO') channel measurement. More specifically, the maximum delay time of a channel using a Gold code or a Kasami code The purpose of the present invention is to provide a method for measuring an accurate MIMO channel without the influence of interference by selecting Spread (LOS) and then selecting a loosely-synchronous (LS) code having an appropriate Interference Free Window (IFW).

MIMO communication system is a system that can transmit data at high speed by using multiple antennas and is suitable as next generation communication system that multimedia data such as video is expected to be the dominant. The MIMO communication system has a larger performance change depending on the characteristics of the channel than the conventional communication system.

The eigenvalues and rank of the MIMO channel matrix or the statistical independence of the channel matrix elements greatly influence the performance of the MIMO communication system. Therefore, accurate measurement of the MIMO channel is essential for the use of such a MIMO communication system.

The measurement of the MIMO channel requires a plurality of antennas at the transmitter and the receiver.

1 is a diagram illustrating a transmitting antenna and a receiving antenna in a conventional MIMO channel environment.

The signal coming into the receiving antenna is in the form of the sum of the signals transmitted from each transmitting antenna. For example, the signal y1 received by the first receive antenna of FIG. 1 is added after the signals of the respective transmit antennas pass through channels h11, h12, ... h1nT, respectively, and the received signals of the other receive antennas are the same. It is composed of principles.

Equation 1 expressing this is as follows.

The receiving end may calculate the matrix H representing the MIMO channel using the above-described received signals. This MIMO channel matrix H can be expressed as shown in [Equation 2].

The MIMO channel matrix H should be able to distinguish each transmitted signal from the received signal in order to calculate h11, h12, ... hnRnT corresponding to the channel shock response.

2002 B.H. Fleury et al. (B.H. Fleury et al.) Measured the MIMO channel using a TDM (Time Division Multiplexing) structure hereinafter. Here, the TDM structure is a structure in which a plurality of transmit antennas transmit a signal only at a specific allocated time of each antenna, and a signal coming into a receive antenna at a specific time includes only a signal transmitted from one transmit antenna. That is, in the TDM structure, both the transmitting end and the receiving end transmit and receive through a designated antenna at an allotted time using respective switches. At this time, the switching time of the transmitter and the receiver should be synchronized.

The MIMO channel measurement method using the above-described TDM structure has some disadvantages. The MIMO channel measurement method using the TDM structure assumes that there is little change in the radio channel during the divided time interval. Therefore, the MIMO channel measurement method using the TDM structure is difficult to use in a rapidly changing channel. In addition, the signal during the switching time period is not accurate enough and can not be used for channel measurement. In addition, in the TDM structure, the amount of data to be stored for the receiver to increase the channel is increased, so that a problem may occur if the storage capacity of the receiver is not large.

In order to solve this problem, the maximum delay spread of the channel is measured using a Gold code or a Kasami code, and accordingly, a LS (Losely-Synchronous) code having an appropriate Interference Free Window (IFW) is measured. The purpose is to provide a method for selecting accurate MIMO channels without the influence of interference by selecting them.

According to an aspect of the present invention, a method for measuring a MIMO channel at a receiving end of a multiple input multiple output (MIMO) communication system according to an aspect of the present invention includes: (a) using specific code information transmitted through a pilot signal Detecting a maximum value of a maximum delay time for each path constituting the MIMO channel; (b) using the detected maximum value, selecting LS code (Loosely-Synchronous) code that satisfies a specific condition and transmitting the number of transmitting antennas to the transmitting end; And (c) measuring the MIMO channel by receiving the final LS code information selected using the LS code information from the transmitter.

A method for measuring a MIMO channel at a transmitting end of a multiple input multiple output (MIMO) communication system according to another aspect of the present invention, the method comprising: (a) transmitting a pilot signal including specific code information to a receiving end; (b) receiving selected LS code information satisfying a specific condition from a receiving end; And (c) extracting final LS code information according to the selected LS code information and transmitting the final LS code information to the receiver.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention, and like reference numerals designate like parts throughout the specification.

In addition, when a part is said to "include" a certain component, it means that it may further include other components, without excluding other components unless otherwise stated.

Now, a method and apparatus for increasing the accuracy of MIMO channel measurement according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

An embodiment of the present invention is characterized by improving the accuracy of MIMO channel measurement by using a Gold code (or Kasami code) and LS (Loosely-Synchronous (LS)) code.

Here, the Gold code is a code having excellent characteristics of cross-correlation and is used in a CDMA system. In the CDMA system, the channel classification of the user uses an orthogonal property between LS codes. That is, the LS code can be assigned to a user or channel that needs to be distinguished, thereby maintaining orthogonality between the users and the channel.

When there is no phase difference, the LS code has a maximum autocorrelation value, and the cross-correlation value between the LS codes becomes zero. That is, the cross-correlation value between LS codes without phase difference (synchronized) is zero.

The LS code has a section in which there is no interference called an IFW (Interence Free Window, hereinafter referred to as 'IFW'). That is, the LS code has a characteristic in that the autocorrelation value and the cross correlation value become zero in the IFW section.

2 illustrates the autocorrelation value and cross-correlation value of the LS code. The auto-correlation value and the cross-correlation value are zero at the phase difference of up to n chips before and after the phase difference is zero with respect to zero.

As such, the use of the LS code can significantly reduce the interference caused by the multipath and the signals of other users. In other words, regardless of the multipath by its own transmission signal or multipath by other users, the signals by the multipath received in the IFW interval have a correlation value (zero interference) of 0, resulting in a good signal-to-interference ratio. This results in a substantial increase in transmission efficiency.

In addition, since the cross-correlation value of the LS code becomes 0 at a certain interval, the cross-correlation value becomes 0 even in a situation where the signal of other users is not completely synchronized.

The IFW characteristic of the LS code can distinguish signals transmitted by a plurality of transmitting antennas simultaneously without affecting interference, and can accurately measure a channel using the signals.

However, in order to improve the accuracy of the channel measurement by using the IFW characteristic of the LS code, the condition that all channel shock responses that are elements of the MIMO channel H must be less than IFW / 2. If this condition is not satisfied, a large amount of interference occurs at the transmitter and the receiver, resulting in performance degradation.

Therefore, in the embodiment of the present invention, after measuring the maximum delay spread (Maximum Delay Spread) of the channel using a Gold code or Kasami code, according to the LS code having an appropriate IFW according to the accurate MIMO channel without the influence of interference It provides a way to measure.

Hereinafter, a method of increasing the accuracy of the MIMO channel measurement will be described in detail with reference to FIG. 3.

The transmitter transmits the pilot signal including the Gold code to the receiver in order to obtain the maximum delay time value (S300).

Subsequently, the receiving end receiving the Gold code detects the largest value tau _max of the maximum delay time for each path constituting the MIMO channel using the Gold code (S302). In order to accurately distinguish the signals transmitted from the plurality of transmitting antennas, the receiver selects LS code information satisfying the condition that IFW / 2 must be greater than the maximum delay time value and transmits the LS code information to the transmitter in step S304.

The transmitter determines the LS code to transmit to the receiver according to the LS code information transmitted from the receiver (S306). Then, the transmitting end transmits the selected different LS code information from each transmitting antenna to the receiving end. The receiver measures the MIMO channel using the LS code information (S308).

4 is a block diagram illustrating an internal configuration of an apparatus for estimating a channel shock response and calculating a maximum delay time value for each path of a MIMO channel using a Gold code according to an embodiment of the present invention.

4 shows an example in which there is one receiving antenna, and even when there are a plurality of receiving antennas, all the receiving antennas have the same structure as the receiving antenna of FIG.

(F₁₁, F₁₂, . . ...F_1nT)(400)은 Gold 코드의 불완전한 상호 상관값(Cross-Correlation)에 대한 특성으로 인하여 다른 송신 안테나에서 전송한 신호로부터의 간섭 신호를 포함하고 있다. 이를 채널 측정값으로 이용하는 경우, 실제 채널값과 비교할 때 그 정확도가 떨어지게 된다. Channel measured using Gold code

(F ₁₁ , F ₁₂ ,...... F 1 _nT ) 400 includes interference signals from signals transmitted from other transmitting antennas due to the characteristics of incomplete cross-correlation of the Gold code. have. If this is used as the channel measurement value, the accuracy is lowered when compared with the actual channel value.

(F₁₁, F₁₂, . . ...F_1nT)(400) 값은 최대 지연 시간 값을 계산하기 위한 데이터로만 활용을 하게 된다. 이렇게 구한 각 채널의 최대 지연 시간 값 중에서 가장 큰 값이 τ_max(410)가 된다.therefore ,

The value of (F ₁₁ , F ₁₂ ,...... F _1nT ) (400) is used only as data for calculating the maximum delay time value. The largest value among the maximum delay time values obtained in this way is τ _max (410).

Finding an LS code with IFW> 2τ _max is related to the length L of the LS code. If the length of the LS code is L, it is easy to find the LS code whose IFW is L / 8. If the number of transmit antennas is two, it is also possible to find a pair of LS codes having an IFW of L / 4.

5 is a block diagram illustrating an internal configuration of an apparatus for measuring a MIMO channel by transmitting LS code information from a transmitter to a receiver according to an embodiment of the present invention.

The transmitting end transmits the selected LS code information to the receiving end by using each transmitting antenna. The receiving end may obtain the MIMO channel H by associating a signal received from each antenna with each LS code.

(500)은 LS 코드의 상호 상관값이 0인 IFW 내에서 구해졌기 때문에 간섭의 양이 0이 되어

(F₁₁, F₁₂, . . ...F_1nT)(400)와 비교하는 경우 실제의 채널 값과 가깝게 된다.MIMO channel H obtained in this way

Since (500) is obtained in IFW where the cross-correlation value of LS code is 0, the amount of interference becomes 0.

When compared with (F ₁₁ , F ₁₂ ,...... F _1nT ) (400), it is close to the actual channel value.

The embodiment of the present invention can accurately measure MIMO channels without mutual interference even though signals are transmitted simultaneously from a plurality of transmit antennas.

Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concepts of the present invention defined in the following claims are also provided. It belongs to the scope of rights.

By the above-described configuration, the present invention can expect the effect of obtaining accurate channel measurement value without using the TDM structure when measuring the MIMO channel.

In addition, since the present invention does not use a TDM structure, it is possible to measure a rapidly changing channel, and does not require an additional device for synchronizing switching at the transmitter and the receiver, and does not cause a situation in which measurement data should be discarded due to switching transition time. You can expect the effect.

Claims (6)

A method for measuring a MIMO channel at a receiving end of a multiple input multiple output (MIMO) communication system, (a) detecting a maximum value of a maximum delay time for each path constituting the MIMO channel using specific code information transmitted through a pilot signal; (b) selecting LS (Loosely-Synchronous) code information satisfying a specific condition by using the detected maximum value and transmitting the number of transmitting antennas to the transmitting end; And (c) measuring the MIMO channel by receiving the final LS code information selected using the LS code information from the transmitter; MIMO channel measurement method comprising a. The method of claim 1, The specific condition of the step (b) is MIW channel measurement method, characterized in that the Interference Free Window (IFW) / 2 that is the interval without the LS code is larger than the maximum value. The method of claim 1, And the specific code information is Gold code information or Kasami code information. A method for measuring a MIMO channel at a transmitting end of a multiple input multiple output (MIMO) communication system, (a) transmitting a pilot signal including specific code information to a receiving end; (b) receiving selected LS code information satisfying a specific condition from the receiving end; And (c) extracting final LS code information according to the selected LS code information and transmitting the final LS code information to the receiver; MIMO channel measurement method comprising a. The method of claim 4, wherein The specific condition of the step (b) is MIMO, characterized in that the Interference Free Window (IFW) / 2, which is an interval without LS code interference, is larger than the maximum value of the maximum delay time for each path constituting the MIMO channel. Channel measurement method. The method of claim 4, wherein In the step (b), receiving the selected LS code information, extracting different LS code information by the number of transmit antennas using the selected LS code information and transmitting to the receiving end MIMO characterized in that it comprises Channel measurement method.

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